Advanced filter design stops any coffee grounds from escaping into the coffee, ensuring a perfect coffee experience. Once depressed filter automatically separates and isolates the coffee grounds from the coffee so that the brewing process ceases and prevents degradation of the coffee flavour Double wall stainless steel vacuum flask will keep your brew hot or cold for 4-6 hours. Leak proof, double lid with silicon seal keeps drinks safe. BPA, BPS and Phthalate free